Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea.
Department of Animal Life Science, Kangwon National University, Chuncheon, Republic of Korea.
Microbiol Res. 2017 Dec;205:48-58. doi: 10.1016/j.micres.2017.08.008. Epub 2017 Aug 24.
Lactobacillus salivarius is an important member of the animal gut microflora and is a promising probiotic bacterium. However, there is a lack of research on the genomic diversity of L. salivarius species. In this study, we generated 21 L. salivarius draft genomes, and investigated the pan-genome of L. salivarius strains isolated from humans, pigs and chickens using all available genomes, focusing on host adaptation. Phylogenetic clustering showed a distinct categorization of L. salivarius strains depending on their hosts. In the pan-genome, 15 host-specific genes and 16 dual-host-shared genes that only one host isolate did not possess were identified. Comparison of 56 extracellular protein encoding genes and 124 orthologs related to exopolysaccharide production in the pan-genome revealed that extracellular components of the assayed bacteria have been globally acquired and mutated under the selection pressure for host adaptation. We also found the three host-specific genes that are responsible for energy production in L. salivarius. These results showed that L. salivarius has evolved to adapt to host habitats in two ways, by gaining the abilities for niche adhesion and efficient utilization of nutrients. Our study offers a deeper understanding of the probiotic species L. salivarius, and provides a basis for future studies on L. salivarius and other mutualistic bacteria.
唾液乳杆菌是动物肠道微生物群的重要成员，也是一种很有前途的益生菌细菌。然而，目前对于唾液乳杆菌物种的基因组多样性的研究还很缺乏。在本研究中，我们生成了 21 株唾液乳杆菌的草图基因组，并利用所有可用的基因组，重点关注宿主适应性，研究了从人类、猪和鸡中分离出的唾液乳杆菌菌株的泛基因组。系统发育聚类显示，根据宿主的不同，唾液乳杆菌菌株可以明显地分为不同的类别。在泛基因组中，鉴定出了 15 个宿主特异性基因和 16 个双宿主共享基因，这些基因仅在一个宿主分离株中不存在。比较泛基因组中的 56 个细胞外蛋白编码基因和 124 个与胞外多糖产生相关的直系同源基因发现，在宿主适应性选择压力下，这些细菌的细胞外成分已经被全球获得和突变。我们还发现了三个负责唾液乳杆菌能量产生的宿主特异性基因。这些结果表明，唾液乳杆菌通过获得定殖和有效利用营养物质的能力，以两种方式进化以适应宿主栖息地。我们的研究更深入地了解了益生菌物种唾液乳杆菌，并为未来对唾液乳杆菌和其他共生细菌的研究提供了基础。
